On-edge indexable inserts having radiused cutting edges for machining arcuate corners are known in the art for use in end mills, face mills and boring tools, in both positive and negative configurations. In one form, the radius extends uniformly from the cutting edge backwardly for the full width of the insert. Mounting of such insert requires either tilting toward a negative angle or mounting in advance of the tool center line or both in order to provide clearance within the cutting radius for the trailing portion of the insert.
U.S. Pat. No. 4,411,564 discloses an on-edge indexable cutting insert wherein each cutting end of the insert is formed with a convexly curved surface which gradually decreases in area per unit of length as the curved surface proceeds away from the cutting edge so as to form each cutting edge with a convexly curved tip of relatively large radius while leaving a flat and planar locating surface of substantial area on each end of the insert. Such construction accommodates a relatively large radius without unduly reducing the planar surface remaining for registration against a locator at the rear of an insert pocket when the insert is indexed to place the adjacent cutting edge in an inactive position. While such construction accommodates a relatively large corner cutting edge radius for a full 90.degree. which may approximate the thickness of the cutter, the diminishing radius away from the cutting edge does not eliminate a requirement, similar to a uniform radius, to provide clearance for the trailing surface through resort to a more negative or advanced positioning of the insert.